This relates generally to imaging systems, and more particularly, to imaging systems that include image pixels with adjustable spectral responses.
Modern electronic devices such a cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensor such as a photodiode that receives incident photons (light) and converts the photons into electrical signals.
In some imaging systems, broadband pixels such as clear pixels and/or yellow pixels may be used to improve the signal-to-noise ratio (SNR) of an image sensor at lower exposure levels. For example, some imaging systems employ an image sensor having clear, red, and blue pixels, without any green pixels. In this type of imaging system, a green signal is determined based on a weighted subtraction of the red and blue signals from the clear signal. This approach has various advantages, such as high resolving power and freedom from chromatic aliasing and associated color artifacts.
However, conventional image sensors having clear pixels often experience negative effects at high light levels. For example, the higher sensitivity of the clear pixel may be nullified by shorter integration times that are required to avoid clipping. The red and blue exposures become shorter by a corresponding amount, which in turn results in reduced chromatic SNR. Additionally, conventional image sensors having clear pixels require a stronger color correction matrix (CCM) to convert RCB data to sRGB data, which can amplify noise and artifacts.
It would therefore be desirable to be able to provide imaging systems with improved signal-to-noise ratio and reduced amplification of noise and image artifacts.